Default manual image builds to dev-<commit> when no tag is given

A manual run with an empty tag input failed validation. It now uses the
checked-out commit's short SHA, and the workflow input is optional.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitea/workflows/publish-image.yml

@@ -6,8 +6,8 @@ on:
   workflow_dispatch:
     inputs:
       tag:
-        description: "dev-<commit SHA> (7-40 lowercase hex characters, matching the selected source)"
-        required: true
+        description: "dev-<commit SHA> (7-40 lowercase hex characters, matching the selected source); empty uses the checked-out commit"
+        required: false
         type: string
 
 permissions:
@@ -35,7 +35,7 @@ jobs:
         env:
           EVENT_NAME: ${{ github.event_name }}
           GIT_REF: ${{ github.ref }}
-          INPUT_TAG: ${{ github.event.inputs.tag }}
+          INPUT_TAG: ${{ github.event.inputs.tag || inputs.tag }}
           SERVER_URL: ${{ github.server_url }}
           REPOSITORY: ${{ github.repository }}
         run: node scripts/image-publication.mjs

scripts/image-publication.mjs

@@ -9,7 +9,7 @@ export function imagePublication({ event, ref, inputTag, revision }) {
 
   let tag, channel;
   if (event === "workflow_dispatch") {
-    tag = inputTag ?? "";
+    tag = inputTag || `dev-${revision.slice(0, 7)}`;
     const commit = /^dev-([0-9a-f]{7,40})$/.exec(tag)?.[1];
     if (!commit || tag !== tag.trim())
       throw new Error(